@goaty I'm thinking like designing individual homes for each OC on a map, and then invent stuff that's in-between them, making up the history and such as you go?
Although, might I suggest, "I'm Sorry Did You Say Streetmagic?"
it's a GMless city-building story game for two to six players
https://seaexcursion.itch.io/street-magic
just wanted to mention it since it seems on topic